This invention relates to the field of acid ferric sulfate leaching of copper sulfide concentrates.
Under certain circumstances, hydrometallurgical processing of copper sulfide concentrates offers significant technological advantages and capital cost savings over conventional smelting technology, including pollution control systems. Conventional hydrometallurgical and other proposed processes require the addition of reactants, other than the copper concentrates, such as chlorides, ammonia, and nitrates, coupled with the recycling and disposal of these components, which adds further complexity to the process.
Contrary to the conventional hydrometallurgical copper sulfide concentrate processes known in the art, the process of this invention includes an acid ferric sulfate leach which has not been heretofore practical due to the slow reaction kinetics which have been encountered in the leaching step. By way of example, the leaching reaction for all copper sulfide concentrates results in the formation of a tenacious elemental sulfur product. The reaction equation for chalcopyrite is as follows: EQU CuFeS.sub.2 + 4Fe.sup.+3 .fwdarw.Cu.sup.++ + 5Fe.sup.++ 2S.degree.
the resulting nonporous sulfur product layer surrounding each particle of the copper concentrate acts to block the reaction which, as a result, severely limits the amount of copper which can be extracted from the concentrate.
Previous attempts have been made to hydrometallurgically process copper sulfide ores, such as chalcopyrite, by pretreating the copper sulfide concentrates by fine grinding the concentrates prior to leaching. West German Pat. No. 2,061,652, published in Germany on July 6, 1972 by Johannes Gerlach, et al. disclosed the use of a fine grinding mechanism for pretreatment of the copper sulfide concentrates. However, the Gerlach et al. patent required that the particles be shattered by sudden impact to impart lattice deformations which significantly alters the crystalline structure of the particles. The patentees in the German patent incorrectly assumed that the presence of excess energy in the particles would be responsible for enhanced leaching of the sulfide concentrates.
Accordingly, it is an objective of this invention to provide a process for leaching copper sulfide bearing materials employing acidified ferric sulfate solutions.
It is further objective of this invention to employ a pretreatment step of fine grinding the copper sulfide particles.
It is also an objective to provide a process for leaching copper sulfide concentrates without the necessity of adding additional components such as nitrates, chlorides, and the like.